The Vulpera are a great example of how a little creativity can make an Allied Race feel truly unique, even when sharing tons of animations.
I believe Gnolls could follow suit. While they are obviously MUCH smaller than Worgen, and also stockier, I think their skeletons are actually very likely quite similar (Tauren are another candidate I could see sharing a model with).
Now, let's consider what Gnolls could potentially bring TO THE GAME at large, and the Alliance specifically.
My thinking is that, in terms of personality, Gnolls could be 100% humorous. As a very primitive race (certainly more than any other on the Alliance), I could see them being the perfect foil for the other, more serious races. Maybe you run into a Gnoll accompanies Stormwind's army, and constantly belittles their scientific achievements ("Giant tank may be large, but rock-tied-to-spear is TRULY frightening weapon!"). Maybe another Gnoll, in the company of some casters, is in constant bewilderment and keeps interrupting with questions. Or a Gnoll Warlock, whose command over demons is tenuous at best, but they seem content to serve him willingly out of amusement.
I also love the thought of a couple of Gnolls, stationed at some Alliance town that when attacked, they begin running around screaming like maniacs.
Hell, maybe they could even offer a rare insight into just how ridiculous some of the forces we contend with are (upon meeting the forces of the Shadowlands, immediately checking out like "Nope, not messing around with this stuff, I'm going back to hunting boars").
Personally, I think they'd have made a far better pick than Mechagnomes (not to mention more comparable to the Vulpera), but it's certainly not too late to add them. I'd definitely lean into the Hyena aesthetic, and for their mounts, actually maybe boars wouldn't be a bad idea. For the racial leader, I honestly wouldn't even mind it being Hogger, just fully embracing how he keeps getting "killed" but you just can't keep a good Gnoll down.
Make the opening quest just sending you into Stockades, saying Hogger is acting up again and hoping you can calm him down, he keeps trying to incite riots even though all the other prisoners just want to eat their dinner in peace. Every time you start to talk to Hogger, he immediate cuts you off, like "I know why you here. You want mighty Gnoll fighters to help puny Alliance army! Well I won't lead them.", and any time you try to change the subject, he just cuts you off like "I SAID I WON'T LEAD MIGHTY GNOLL ARMY INTO GLORIOUS BATTLE", until finally "Fine, you talk Hogger into it. Gnolls will need finest weapons and salted meats Alliance has to offer. NOW GO!"
As far as Race/Class choices, I think they could probably suit most everything, save for Priests/Paladins, Death Knight, and maybe Demon Hunter (although part of me kind of loves the idea of allowing them as DH, and have the first NPC you run into comment "Wait, how did a GNOLL get here...? Uhh, anyway, here's what we're doing...)
I dunno, I feel like this would honestly just be a pretty great addition to the game. Like I say, just keep them super primitive and humorous, maybe even make them a little bit crazy.